Qatar shares its only land border with Saudi Arabia, and relies heavily on food imports, much of it from Gulf countries.
Arab nations including Saudi Arabia and Egypt on Monday cut ties with Qatar, accusing it of supporting extremism, in the biggest diplomatic crisis to hit the region in years.
Multiple queues up to 25-people deep formed in Carrefour supermarket in Doha's City Center mall, one of the busiest shopping areas in the Qatari capital, hours after five Arab states cut diplomatic ties with the emirate.
Shoppers piled trollies and baskets high and shelves were stripped of essentials such as milk, rice and chicken.
Among the hundreds of shoppers desperately searching for staple goods was Azir, a Sri Lankan who went to the store when relatives called him from home after watching the news on television.
"I was asleep. My family phoned me and woke me up from Sri Lanka," he said, his trolley full of nappies for his 18-month-old child.
"I came because of the crisis."
Qatar imports goods such as chicken from Saudi Arabia, and locals quickly took to social media on Monday to complain they would have to eat poultry from Oman instead.
Ernest, from Lebanon, said he knew he had to go shopping because others would rush to the shops.
"It's a cycle of panic and I needed to get pasta," he said, as he shopped with his young family -- pushing not one but two trollies.
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The story was the same across town at one of the several Monoprix stores, where staff said it had been one of the busiest days at work they had known.
In the nearby Al-Meera supermarket, shoppers again packed the store, including Denis from Germany who was convinced that the crisis was just a temporary storm.
- 'Just a yellow card' -
"This is just a yellow card," he said of the country due to host football's 2022 World Cup.
"What can they do? It is one of the richest countries in the world."
To try to avoid widespread panic-buying, Qatar's government issued a statement claiming that shipping routes and airspace will remain open for imports.
The "Qatari Government will take all necessary measures to... thwart attempts to influence and harm the Qatari society and economy," the statement said.
One sector of the economy which could be badly hurt is exports, including goods such as machinery, electronic equipment or livestock transported by road to Saudi Arabia.
According to the United Nations, Qatari exports to Saudi Arabia totalled $896 million (796 million euros) in 2015.
The severing of ties is also potentially bad news for the service industry, including hotels and cab drivers in Doha.
Saudis usually flock to Qatar on holiday during Eid al-Fitr at the end of the Muslim holy fasting month of Ramadan.
But with a travel ban now imposed by Riyadh, takings could be down for many south Asian cab drivers who rely heavily on tourists.
"This is very bad news, very bad news," said Raihan, a driver from India. "All Saudis come here for Eid."